What tool do technicians use to check for electrical potential at a switch or load?

The most appropriate tool for checking electrical potential at a switch or load is a voltmeter. A voltmeter is specifically designed to measure the voltage, or electrical potential difference, across two points in an electrical circuit. By connecting the voltmeter probes to the points of interest, technicians can determine if there is adequate voltage present for the device to operate properly.

In contrast, an ammeter measures current flow in a circuit, which is not useful for assessing potential. A micrometer is primarily used for measuring small distances or dimensions with high precision, making it unrelated to electrical potential. An ohmmeter measures resistance in an electrical circuit, but again, this does not provide information about voltage levels. Thus, for checking voltage at a switch or load, a voltmeter is the correct and relevant tool to use.